#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int n, m;

void solve()
{
    cin >> n >> m;
    multiset<int> ms1, ms2;
    for (int i = 1; i <= n; ++i)
    {
        int x;
        cin >> x;
        ms1.insert(x);
    }
    for (int i = 1; i <= m; ++i)
    {
        int x;
        cin >> x;
        ms2.insert(x);
    }
    vector<int> ans;
    ll need = 0;
    int mm = 2e9;
    while (ms2.size())
    {
        if (*ms2.rbegin() < *ms1.rbegin())
        {
            cout << "-1\n";
            return;
        }
        need += *ms2.rbegin() - *ms1.rbegin();
        mm = min(mm, *ms1.rbegin());
        for (int i = *ms2.rbegin() - 1; i >= *ms1.rbegin(); --i)
        {
            ans.push_back(i);
            if (ans.size() > n - m)
            {
                cout << "-1\n";
                return;
            }
        }
        ms2.erase(prev(ms2.end()));
        ms1.erase(prev(ms1.end()));
    }
    if (ms1.size() < need)
    {
        cout << "-1\n";
        return;
    }
    vector<int> v;
    while (ms1.size() > need)
    {
        int x = *ms1.begin();
        ms1.erase(ms1.begin());
        ms1.insert(x + 1);
        v.push_back(x);
        if (*ms1.begin() > mm)
        {
            cout << "-1\n";
            return;
        }
        ms1.erase(ms1.begin());
    }
    reverse(ans.begin(), ans.end());
    for (auto e : ans) v.push_back(e);
    cout << v.size() << '\n';
    for (auto e : v) cout << e << ' ';
    cout << '\n';
    return;
}

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int T = 1;
    cin >> T;
    while (T--) solve();
    return 0;
}